NPR Story

How To See Forever On Your Dirty Car

When you're in love with science, ordinary everyday stuff can suddenly seem extraordinary. At least that's how NPR blogger and astrophysicist Adam Frank sees it, even down to the dust on his car.

ADAM FRANK, BYLINE: Carl Sagan, an astronomer with the soul of a poet, liked to remind us that we are all star stuff. It was without a doubt one of his most beautiful images. But what really was Carl Sagan talking about? Well, there are two answers to this question.

The first is remarkable and the second is crazy-remarkable. And if we pay attention, both can open a hidden doorway for us to depths of time that we swim through every day without ever noticing. Let's unpack the remarkable answer first. Every atom in your body was produced in space eons ago. The simplest kinds of atoms like hydrogen date back to the universe's Big Bang beginnings 13.7 billion years ago.

Everything else - carbon, oxygen, iron, et cetera - they were all born in the furnace of a star once stars began to form about a billion years after the Big Bang. So what Carl Sagan was telling us is that stars aren't just out there in space. The stuff of stars is right here on Earth, right now. But now comes the even crazier point, and this is the one that links the Earth directly to the heavens. How did all of that star stuff get here? And by here, I mean right here, the very earth you stand on. The answer, my friends, is dirt, space dirt.

Five billion years ago, the solar system was nothing more than a vast disc of gas and dust swirling around the newly-formed sun. The gas was free-floating atoms, but the dust - ah, the dust - that was already something more. The tiny flecks of solid matter, the lowly grains of minerals of space dirt, they were the keys to assembling planets. It started with tiny coalitions, two grains of dust sticking together and making a bigger grain.

Eventually, the bigger grains collided and stuck together to make pebbles. Then the pebbles made rocks, and the rocks made boulders and the boulders made mountain-sized asteroids floating through space, all the way up to the beautiful blue-green world you're sitting on right now. So go ahead, pick up a clod of earth and you are without doubt cupping a handful of space dirt that once floated free in the inky darkness four to five billion years ago. Unless of course it just arrived. See, that's one of the freaky parts of the story. The space dirt is still coming. And if this seems too crazy and you don't believe me, just go out and look at that dirty car you're driving around.

Every year, almost 100,000 tons of space dirt falls on our planet. That's the equivalent of one U.S. Nimitz-class aircraft carrier dropping from the skies every year. Of course, it doesn't all come at once. Each day, about a hundred tons of material hits the Earth. Most of it is in the form of interplanetary dust caught in the Earth's gravitational pull. But on any given night, you might also catch the bigger stuff: sand-grain-sized or even pebble-sized bits of the solar system flaring across our sky as meteors. After their fiery journey through the atmosphere, most of that material ends up as dust on the ground too.

So if you do the math - and I just did - those hundred tons of inbound space stuff translates into about 10,000 grains of dust added to your car every day. And if, like me, you only make it to the car wash once a year, then odds are pretty good that if you write, clean me, on your car's rear window, it will leave at least a few tiny bits of dusty space dirt on your fingers. And it's right there, on your fingertips, that you can meet eternity up close.

CORNISH: Adam Frank teaches physics at the University of Rochester and blogs for us at npr.org. Transcript provided by NPR, Copyright NPR.